update imports from golang.org/x/tools

v0.0.4

commit 535c3a4 (HEAD -> master, origin/master)
Author: Charlie Vieth [email protected]
Date: Wed Sep 8 11:45:31 2021 -0400

ignore vendor directory

commit 65a21c1
Author: Charlie Vieth [email protected]
Date: Fri Sep 3 12:38:55 2021 -0400

skip failing mod tests with the '-short' flag

TODO: fix these tests - I'm guessing it has something to do with the
test setup.

commit 22a11b6
Author: Charlie Vieth [email protected]
Date: Fri Sep 3 00:00:17 2021 -0400

cache: move code to separate file and simplify key

This commit moves the cache to it's own file and changes it to use a
simpler key.

commit 459e429
Author: Charlie Vieth [email protected]
Date: Tue Aug 31 20:13:32 2021 -0400

update golang.org/x/tools/internal and modules

Update the tools we use from golang.org/x/tools/internal and our
modules.

commit 59ff746
Author: Charlie Vieth [email protected]
Date: Wed Mar 24 15:28:30 2021 -0400

add xbench package for benchmarking imports

* `go test -bench . -benchmem -count 10`